engleski

Where to inject botulinum toxin in the treatment of pain?

Objective: Recently botulinum toxin type A (BTX-A) has been used to treat various pain syndromes. One of the intriguing and clinically important question is where to inject BTX-A. In the present study in rats we investigated: 1. whether antinociceptive effect of BTX-A is segmental and 2. if BTX-A is effective when injected into the sensory ganglia. Design and Methods. Male Wistar rats were injected into the right forepaw pad with BTX-A 7 U/kg while the second group received the same dose in the right hindpaw. Control group was injected with saline. After 5 days all groups were injected into the righ hindpaw-pad with formalin (5%). The number of flinches of the injected paw was counted over 60 min. In the second series of experiment BTX-A 0.5 U/kg was injected into the right trigeminal ganglion. Control rats received saline. After 2 days formalin (2.5%) was applied into the right upper lip. The number of seconds that the animals spent rubbing the injected area was recorded and data analysed by Newman-Keuls post hoc test. Results. BTX-A, injected into the hindpaw-pad, significantly reduced the flinches induced by formalin. Number of flinches was 280.7&#177; 9.5 for control vs. 200.6&#177; 13.7 for BTX-A (p<0.05). However, BTX-A was ineffective when injected into the right forepaw-pad (number of flinches was 260.2&#177; 31.3). Intraganglionic injection of BTX-A 0.5 U/kg significantly reduced rubbing time in the second phase of the formalin test (591.9&#61617; 26.1 s for control group vs. 444.3&#61617; 31.3 s for BTX-A-treated group ; p<0.01). Conclusion. Here we show that antinociceptive effect of peripherally applied BTX-A is limited within the innervation segment of particular sensory nerve. In line with that, antinociceptive effect of BTX-A could be achieved after direct injection into sensory ganglia. However, this oppose suggested peripheral mechanism of antinociceptive action of BTX-A. Supported by Croatian MZOS (108-1080003-0001 and 108-1080003-0020) and DAAD.

botulinum toxin; pain; nociception

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